The use of locks of known designs and configurations are known in the prior art. More specifically, locks of known designs and configurations heretofore devised and utilized for the purpose of minimizing the possibility of opening locks without keys are known to consist basically of familiar, expected, and obvious structural configurations, notwithstanding the myriad of designs encompassed by prior designs which have been developed for the fulfillment of countless objectives and requirements.
By way of example, U.S. Pat. No. 1,414,348 to M. Falk discloses a pin-tumbler lock. U.S. Pat. No. 3,478,549 to E. L. Schlage discloses a pick resistant lock unit. U.S. Pat. No. 3,531,959 to E. Weber discloses a security attachment for cylinder lock. U.S. Pat. No. 4,103,526 to Surko, Jr. discloses a pin tumbler lock. U.S. Pat. No. 4,631,941 to Sjunnesson discloses a cylinder lock with permissible service entry. U.S. Pat. No. 4,953,375, to Tzou discloses an electronically self-latching cylinder lock. U.S. Pat. No. 5,361,614, to Metcalf discloses a pin-tumbler lock with retained key and method of operation thereof. U.S. Pat. No. 5,400,629 to Myers discloses an axial pin tumbler lock. U.S. Pat. No. 5,640,865 to Widen discloses a cylinder lock and key combination. Lastly, U.S. Pat. No. 5,475,997 to Chung discloses a lock assembly.
Most lock mechanisms in use include a housing having a generally cylindrical bore therethrough in which is mounted a revolving cylinder or tumbler. A plurality of biased pins or plungers are provided which cooperate with the housing and the revolving cylinder to enable or inhibit the rotation of the tumbler, the plungers or pins being arranged to detect a suitably coded key which actuates one or more of these plungers or pins. With most commonly used constructions, the revolving cylinder or tumbler is mounted in a through bore of the housing, and the keyhole which accepts the key extends substantially through the revolving cylinder. The pins or plungers are typically arranged along the axis of the tumbler and engage the key as the same is moved into the keyhole.
Structures are generally provided in the lock core for maintaining the pin holes in the core in axial alignment with the pin holes in the cylinder so that the driver pins are free to pass through the shear line between the core and the cylinder and into the cavities holding the follower pins. When a key designed for the lock is inserted into the key slot in the cylinder, the key engages the follower pins and moves them to a position where the abutting faces of the pins lie along the shear line between the core and cylinder, permitting the core to be rotated with respect to the cylinder by rotation of the key.
A problem which exists with most lock cylinders in use today is that the above-described constructions make it possible for the locks to be violated by picking or partially destroying the same. Picking of such locks has been facilitated by the fact that the plungers or pins are arranged in line with the keyhole and, therefore, are readily accessible to one who is skilled in picking such locks. This traditional type of lock can be very susceptible to being picked, or unlocked by unauthorized persons, by inserting a wire, or other elongated instrument, or instruments, which can be manipulated in such a way as to simultaneously place a rotational force on the core of the lock while moving the follower pins, one at a time, into shear alignment with the peripheral surface of the core. The rotational force is necessary in order to capture a follower pin in its shear position while manipulating the other such pins of the lock, until all are in proper alignment to allow the core to be rotated.
Other locks have the decoding pins or plungers situated proximate to the keyhole or to the keyhole opening so that their operation may be destroyed by drilling into one or another portion of the revolving cylinders. Most typically, revolving cylinders of this type may be made inoperative by simply drilling a hole along the axis of the keyhole and thereby destroying the decoding means or the pins and plungers, which are arranged to sense the key.
Various attempts have been made to overcome the above-mentioned problems and to minimize the risk of having a lock picked. Some early attempts at overcoming the problem are exemplified in U.S. Pat. Nos. 866,697 and 888,478. In the first mentioned patent, a key was used which had a bifurcated resilient member at one end thereof which was adapted to engage a suitable actuating mechanism within the lock. The portions making up the bifurcated end of the key were slightly spaced from the axis of the key. This lock did not, however, utilize a cylinder of the type commonly used today and did not use pins or plungers. Instead, the lock of this reference utilized a sliding latch arrangement, which did not provide much protection against picking. The bifurcated end of the key was initially compressed by a channel of reduced diameter, which was in turn provided with a pair of slots internally of the lock, which permitted the bifurcated end to expand when brought into registry with the slots. At such time, the bifurcated end could engage and actuate the latch mechanism.
U.S. Pat. No. 888,478 was for a lock design that utilized a double key, one portion having a straight shank and the other portion having a curved shank, with both portions being pivotally connected to each other. Before the latch mechanism of this lock could be actuated, it was necessary to insert the key in such a manner so that both straight and curved shank portions engaged respective or cooperating elements within the lock.
Other attempts have been made to produce a pick-proof lock. These have included locks which use a key having a pivoted free end which is adapted to turn or rotate a predetermined angular distance upon full insertion of the key into the lock to engage an element which would not otherwise be engageable by a straight shank. In U.S. Pat. No. 1,596,336, for example, a lock is disclosed which uses a key having a pivoted end member which is initially aligned with the shank of the key in one position thereof. When the key is turned approximately 180 degrees, the pivoted end portion moves, due to gravity, to a position that permits the same to engage a latch. Further rotation of the key causes the latch to move. In order to provide somewhat more control over the action of the key, and more particularly over the pivoted free end thereof, further constructions have been proposed wherein the position of the pivotally mounted free end may be controlled at the exposed end of the key or in the region of the gripping portion thereof. Such constructions are disclosed in U.S. Pat. Nos. 1,464,194 and 1,750,542. In all of these patents, however, the movement of the pivoted end towards the final or operative position only causes the pivoted portion to engage a latch or the like and could not, in and of itself, be utilized with the more modern and more complex locks which are in use today.
Other locks which are known in the prior art include a key which has a pivotally mounted finger thereon, the finger itself being provided with a cam surface which engages an abutment upon insertion of the key into the cylinder to cause the finger to be deflected from its initial axially aligned position to one where the fingers may be displaced approximately 90 degrees from that initial position. In U.S. Pat. Nos. 1,274,313 and 2,296,029, these pivotally mounted fingers engage a latch mechanism in the pivoted or actuating position, while in U.S. Pat. No. 1,567,979, the finger engages a pair of spring-loaded pins or plungers. The last described construction has the disadvantages above described since the spring loaded pins or plungers are mounted substantially in line with the keyhole and, therefore, this allows for the lock to be defeated by simply drilling through the keyhole.
Another such lock is described in U.S. Pat. No. 2,596,720 in which the spring-loaded driver pins are provided with reduced diameter terminations abutting spacer disks or different diameter balls riding on an associated tumbler pin. In accordance with this design, each of the bores of the core are flanked by two relatively shallow recesses, or grooves, extending over a limited arch of the periphery of the barrel, or core, the depth of the grooves increasing toward the extremities remote from each bore to form an abutment. Accordingly, when an attempt is made to pick the lock, the core will begin to rotate as soon as the top of a disk lies flush with its periphery. The end terminations of the driver pins now ride in the grooves, and the maximum angle of rotation, which will be reached after all the tumbler pins have been picked, is fixed by the abutments, which is insufficient to retract a latch controlled by the lock. It can thus be seen that each of the aligned tumbler bores must carry a plurality of relatively small components or elements, some of which must be relied on to carry extreme shear load in the case where an attempt is made to pick the lock.
As noted above, many traditional lock assemblies have inherent shortcomings in that they are highly susceptible to being xe2x80x9cpickedxe2x80x9d by skilled individuals. There are a number of approaches to lock-picking, but most are built around the idea of imparting a certain level of random motion to the pins while placing a certain level of torque on the lock cylinder. With this approach, pins in the appropriate (xe2x80x9cunlockedxe2x80x9d) positions are often more likely to stay in their appropriate positions, while pins in inappropriate (xe2x80x9clockedxe2x80x9d) positions are slightly freer to move, and are likely to continue doing so under the influence of the applied random motion.
The lock of the present invention incorporates a lock cylinder having a number of features designed to defeat attempts to pick or destroy the lock. First, in certain embodiments the lock cylinder assembly employs two or more separate arrays of pass key pins. With this arrangement, a person attempting to pick the lock cylinder assembly would have to contend with all pin arrays simultaneously, rather than only a single pin array as found in many earlier designs. Rotation of the cylinder blank in the cylinder bore can only be performed when all of the pass key pins are properly aligned along the shear lines of the lock cylinder assembly. Placing the pins in separate arrays makes picking of the lock cylinder assembly more difficult as compared to picking of a more traditional lock cylinder assembly having its pass key pins aligned in a single array.
In addition to the advantages described above, certain embodiments of the lock assembly of the present invention incorporate certain features designed to prevent the defeat of the lock cylinder by destructive means. It is known that traditional lock cylinder assemblies can be defeated through the use of drills or similar metal-cutting tools to either destroy the pass key pins or remove the surrounding material to allow removal of the pass key pins. Certain embodiments of the lock assembly of the present invention incorporate a number of features designed to thwart the defeat of the lock cylinder assembly through such methods. First, the arrangement of the pass key pins in separate arrays requires that separate cuts be made into the lock housing mogul or cylinder blank in order to defeat the lock cylinder assembly. Second, certain embodiments of the lock assembly of the present invention incorporate separate sets of hardened dowel pins to prevent drilling through the lock housing mogul in the area of the side driver pins and top driver pins. Third, certain embodiments of the lock assembly of the present invention incorporate a hardened cylinder shield behind the front face of the cylinder blank to prevent drilling through the cylinder blank in the area of the top pass key pins or the side pass key pins. In certain embodiments of the present invention, the cylinder shield is designed so that the area protected by the cylinder shield partially or completely overlaps the area protected by the dowel pins.